Molecular Basis of Automaticity in the Myometrium

描述(申请人提供)：早产(PTB)，在怀孕37周之前，显著增加了长期并发症的风险，如神经发育障碍、智力低下、脑瘫、失明、耳聋和呼吸系统疾病，以及沟通和行为障碍。虽然一些危险因素是已知的，但30-50%的自发性肺结核的病因不明。子宫收缩，就像所有的平滑肌收缩一样，主要是一种机电事件，即电信号启动收缩。虽然激素和生化途径在分娩条件的形成中起着关键作用，但子宫兴奋-收缩耦合的速度和协调性表明，分娩中兴奋的短期协调信号是由离子通道携带的。妊娠期间子宫肌层电行为的改变必须是由贡献离子通道的表达水平或行为的变化引起的。因此，自发性肺结核反映了子宫电活动发育的异常时间。分娩期间的收缩是由子宫肌层固有的节律性电活动(起搏)引起的。兴奋收缩耦合的基本成分之一是起始性去极化，即“起搏器”电流。这一建议是基于我对子宫起搏器电流的潜在分子基础的发现。我的初步数据显示，子宫中有一类独特的离子通道，即超极化激活的环核苷酸敏感(HCN)阳离子通道。在其他组织中，这些通道设置静息电位并产生有节奏的放电活动，即参与起搏和自律性。我的初步数据显示，与未怀孕的子宫肌层相比，妊娠晚期子宫组织中HCN1基因的表达上调了约150倍，而HCN4的转录下调了约50倍。HCN1通道的激活速度比HCN4通道快约10倍，并且在去极化的~30 mV时被激活，这表明HCN介导的自发电活动在妊娠晚期显著增加。这种与妊娠相关的HCN通道亚型的戏剧性上调是最容易和最快激活的(HCN1)，假设导致自发的肌层兴奋增加，从而导致收缩。我的假设是，hcn1基因的上调有助于怀孕子宫的起搏。本研究的目的是从分子水平鉴定子宫肌层中的HCN通道异构体，并对相应的细胞电流进行电生理学鉴定和表征。早产导致巨大的医疗、社会、情感和经济成本。目前，还没有有效的方法来预防早产。离子通道是子宫起搏器，它的识别为设计预防和延迟早产的干预措施提供了机会。早产导致巨大的医疗、社会、情感和经济成本。目前，还没有有效的方法来预防早产。离子通道是子宫起搏器，它的识别为设计预防和延迟早产的干预措施提供了机会。

DESCRIPTION (provided by applicant): Preterm birth (PTB), prior to the 37th week of gestation, significantly increases the risk of long-term complications such as neurodevelopmental disabilities, mental retardation, cerebral palsy, blindness, deafness and respiratory diseases, as well as communication and behavioral difficulties. Although some risk factors are known, 30-50% of spontaneous PTBs have an unknown etiology. Uterine contraction, like all smooth muscle contraction, is primarily an electromechanical event, i.e., an electrical signal initiates contraction. Although hormonal and biochemical pathways play key roles in developing parturition conditions, the speed and co-ordination of uterine excitation-contraction coupling indicates that the short-term coordinating signals for excitation in labor are carried by ion channels. The alteration of the electrical behavior of the myometrium during gestation must arise from changes in the expression level or behavior of the contributing ion channels. Spontaneous PTB therefore reflects abnormal timing in the development of the electrical activity of the uterus. Contraction during parturition results from rhythmic electrical activity (pacemaking) intrinsic to myometrium. One of the fundamental components of excitation-contraction coupling is the initiating depolarization, i.e., the "pacemaker" current. This proposal is based on my findings of a potential molecular basis for a uterine pacemaker current. My preliminary data show a unique class of ion channels, Hyperpolarization-activated Cyclic Nucleotide-sensitive (HCN) Cation Non-selective channels, in the uterus. In other tissues, these channels set the resting potential and generate rhythmic firing activity, i.e., are involved in pacemaking and automaticity. My preliminary data show that HCN1 mRNA expression is upregulated ~150 fold and HCN4 transcript is downregulated ~50 fold in late gestation relative to non-pregnant myometrium. HCN1 channels activate ~10 fold faster and are activated at a potential ~ 30 mV more depolarized than HCN4 channels, suggesting a major increase in HCN-mediated spontaneous electrical activity in late gestation. This dramatic pregnancy related upregulation of the HCN channel isoform which is most easily and rapidly activated (HCN1), is hypothesized to result in increased spontaneous myometrial excitation and consequently contraction. My hypothesis is that the upregulation of HCN1 mRNA contributes to pacemaking in the pregnant uterus. The aim of this proposal is to molecularly identify HCN channel isoforms in the myometrium and to electrophysiologically identify and characterize the corresponding cellular currents. Preterm birth results in enormous medical, social, emotional and financial costs. Currently, there are no effective ways to prevent preterm birth. Identification of an ion channel which is the uterine pacemaker offers the opportunity for designing interventions to prevent and delay preterm labor. Preterm birth results in enormous medical, social, emotional and financial costs. Currently, there are no effective ways to prevent preterm birth. Identification of an ion channel which is the uterine pacemaker offers the opportunity for designing interventions to prevent and delay preterm labor.